Ac Adapter Tips

An AC adapter allows a laptop computer to be plugged into a standard wall outlet. It converts the "AC" (or "alternating current") of a wall outlet to "DC" (or "direct current") so the laptop can draw power safely while charging the battery. Usually, an AC adapter is built to last for years, but sometimes it does not last as long as planned. When caring for or replacing a faulty AC adapter, there are a few things to keep in mind in order to maximize its usefulness and compatibility.
AC Adapter Compatibility Not all AC adapters are created equal. Some will have differing input and output voltages which makes choosing the correct one frustrating. If you are replacing a laptop's adapter, always check its specifications to determine the power requirements. Also, laptop computers have different sized DC plugs, so make sure that the adapter that you buy will fit. Many universal AC adapters come with interchangeable plugs to prevent this problem.
General Tips
An AC adapter's secondary function is to charge a computer battery. A full charging session takes around two hours or longer if you use the computer during that time. If the battery is completely dead, you may need to leave the adapter plugged in for a few minutes before you turn on the computer.
Avoid exposing an AC adapter to prolonged periods of extreme heat or cold. Doing so could damage the internal circuitry and prevent it from working. Always wrap up the AC cord tightly when traveling, and avoid any contact with other metallic devices, like coins, pens or paperclips. These could accidentally short-circuit the adapter by causing an connection of the positive an negative terminals, for example, when bouncing around in a bag.
Specifications
AC adapters come in hundreds of sizes, shapes and ratings, but three factors count most.
Voltage: Adapters typically provide between 3 and 24 volts.
Current rating: Electronic items typically consume between 100 and 3,000 milliamps. The adapter provided with the electronic item will deliver enough current, but no more,
Plug type and polarity (the plug that goes into the gadget, not the wall): Most adapters have two-conductor plugs, some have three. You can have an adapter with the right voltage and current, but if the plug's wrong, you're stuck. Polarity also varies among different models; some have a positive internal pin with a negative outside, some have it the other way around. A multi-use adapter allows you to switch polarity, so it will work with the widest range of equipment.
Testing
If you have a piece of equipment that's working poorly, the cause might be its AC adapter. You can check the voltage and polarity easily with a handheld multimeter. If you're lucky enough to have an oscilloscope, use it to test the adapter. Look for excessive ripple (bad capacitors) or lack of DC offset (bad diodes). If you find anything amiss with the adapter, simply replace it with an equivalent.